The descent and landing were called “seven minutes of terror.” Since that white-knuckle event, NASA’s Curiosity rover has had a little longer than half a Martian year of quiet wonder. But in Earth years, it’s an anniversary: Curiosity touched down on Mars early on August 6th, Earth Eastern time, 2012, setting off a jubilant celebration at NASA’s Jet Propulsion Laboratory.

Since then, the plutonium-powered robot has logged more than one kilometer of driving on Mars. It has photographed what looks to be an ancient, gravely streambed. And it has drilled into sedimentary rocks and consumed the powdery extract to analyze its composition. Those rocks bear traces of an ancient wet environment where “conditions once were favorable for life,” according to project scientist John Grotzinger.

The rover has even gulped a bit of Martian air to measure its composition. As of yet, Curiosity has not detected any methane—its presence might point to ongoing biological activity on the Red Planet. But the evidence gathered indicates that Mars may well have been habitable at some point in its history.

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